1. Field of the Invention
The present invention is directed to a programmable, configurable bus system of lines to interconnect electrical components for an electrical/electronics system.
2. Art Background
Megacells are described as block components such as static random access memory (SRAM), microcontrollers, microprocessors and buffers. Sometimes it is desirable to interconnect a plurality of megacells together to provide a larger functional entity. One way to interconnect multiple megacells and logic circuits is through a hardwired bus system. Examples are illustrated in FIGS. 1a, 1b and 1c. FIG. 1a illustrates a bus interface to a dual port SRAM megacell. Bus lines include DATA 0-DATA15, READA0-READA9, WRITEA0-WRITEA9. To couple multiple megacells, the data lines are shared among the coupled cells. However, separate read and write lines would be required for each megacell. To the contrary, if the megacells were coupled to generate a deeper combined megacell, the data lines would be separate for each megacell and the read and write lines would be shared among the megacells. Control signals are then be used to select a particular megacell for a particular operation. This is illustrated in FIGS. 1b and 1c. 
Such configurations are hardwired and cannot easily be changed to accommodate different configurations. Furthermore, if errors occur in the mask generated, repairs are not easily made, as configurability is minimal. In addition to providing a bus system to interconnect multiple megacells, tristatable input ports are sometimes used to enable multiple inputs to be input to a particular bus line thus allowing a system level communication between logic to megacells or megacells to megacells. However, a single tristate can directly couple to only one line.